Key facts
- Brand
- Siemens
- Model
- QFM31
- Industry
- Industrial
- Documents
- 2
- Languages
- ZH
- Last added
- 2000-01-01
Start here
Siemens QFM31 Duct Sensor User Manual
The QFM31 series duct sensors from Siemens are designed for high‑accuracy relative humidity and temperature measurement in HVAC applications. The manual describes the sensor’s capacitive humidity principle, temperature measurement ranges, and the available DC 0‑10 V or 4‑20 mA output signals.
Installation guidelines cover mounting the sensor in the middle of a duct, required clearances from steam humidifiers, wiring recommendations (shielded twisted pair, cable length limits), and safety considerations such as using a SELV transformer and maintaining IP65 protection. This manual is written in Chinese.
Siemens QFM31 specifications
| Working voltage | AC 24 V ±20 % or DC 13.5‑35 V |
|---|---|
| Humidity measurement range | 0‑100 % RH |
| Temperature measurement ranges | ‑35…+35 °C, 0…50 °C, 0…70 °C |
| Humidity accuracy | ±2 % RH |
| Temperature correlation | ≤ 0.05 % RH/°C |
| Time constant | ≈ 20 s (air flow) |
| Output signal (humidity) | DC 0‑10 V or 4‑20 mA |
| Output signal (temperature) | DC 0‑10 V or 4‑20 mA |
| IP protection rating | IP65 |
All Siemens QFM31 documents by type
Day-to-day operation, settings and troubleshooting. Start here if the product is already set up.
Questions answered in these manuals
What are the recommended wiring practices for the sensor?
Use shielded cable, route signal and power lines as twisted pairs, keep cable lengths within the allowed range, and follow EMC guidelines in noisy environments.
What is the working voltage for the QFM3160 sensor?
The sensor can be powered from AC 24 V ±20 % or DC 13.5‑35 V.
What is the humidity measurement accuracy?
The humidity accuracy is ±2 % over the range 0‑100 % r.h. at 23 °C.